This application claims the priority of Japanese Patent Application No. 6-110496 filed on Apr. 25, 1994.
1. Field of the Invention
The present invention relates to a film loading apparatus for a camera and, more particularly, to the structure of a film loading apparatus which uses a planet gear for switching between an initial film feeding operation and a film rewinding operation by the movement of the planet gear.
2 Description of the Related Art
In a camera, a motor is used not only for a film winding operation for winding a film for every exposure, but also for an initial feeding operation for winding a predetermined amount of the forward end of the loaded film around a take-up spool and setting the film ready for photographing, and for a film rewinding operation for rewinding the film into the patrone after it is fully exposed. It is possible to select the initial feeding operation or the rewinding operation by switching a planet gear.
FIG. 4 is a bottom view of the structure of a conventional film loading apparatus for a camera. In FIG. 4, a fork gear 1 which engages a film patrone take-up shaft and a rewinding gear 2 which meshes with the fork gear 1 are provided on the right-hand side, and a spool 4 for taking up film 3 is provided on the left-hand side. The pinion 5 of a motor is connected to the spool 4 via a plurality of gears, and a planet gear mechanism including a sun gear 6 and a planet gear 7 meshes with the pinion 5. The planet gear 7 slides along a guide groove 8.
One-tooth sprocket 10 having a pawl tooth 9 is integrally provided with a feeding gear 11 in such a manner that the pawl tooth 9 engages a perforation of the film 3. Since the planet gear 7 slides along the guide groove 8 in accordance with the direction of rotation, the planet gear selectively meshes with the rewinding gear 7 and the feeding gear 11.
According to the above-described structure, when the spool 4 is rotated clockwise (hereinunder referred to as "normally") by the motor, the sun gear 6 is normally rotated and the planet gear 7 is thereby rotated counterclockwise (hereinunder referred to as "reversely"). The planet gear 7 then moves to the position indicated by the solid line and meshes with the feeding gear 11 so as to rotate the one-tooth sprocket 10 clockwise. By the rotation of the one-tooth sprocket 10, the forward end of the film 3 is fed toward the spool 4 and the fed film 3 is taken up by the spool 4. On the other hand, if the motor is reversely rotated when the film 3 is fully exposed, the sun gear 6 is reversely rotated, and the planet gear 7 moves to the position indicated by the broken line so as to mesh with the rewinding gear 2. In this case, the fork gear 1 is rotated counterclockwise, thereby rewinding the film 3 into the patrone. In this manner, if the planet gear 7 is used, it is possible to selectively switch between the initial film feeding operation and the film refunding operation by changing the direction of rotation of the motor.
In the above film loading apparatus, however, there is a problem that the planet gear 7 which engages the feeding gear 11 is sent flying toward the rewinding gear 2 at the time of initial film feeding. More specifically, when the film 3 is fed by the one-tooth sprocket 10, since the pawl tooth 9 engages a perforation and therefore a load is applied to the one-tooth sprocket 10, the rotation of the one-tooth sprocket 10 is slow. When this engagement is released, the one-tooth sprocket 10 suddenly rotates at a high rate. When the one-tooth sprocket 10 and the feeding gear 11 suddenly rotate at a high rate, the planet gear 7 is disengaged from the feeding gear 11. In another case, when the pawl tooth 9 is not smoothly engaged with a perforation and it is engaged with the perforation after strongly pressing the film 3, the reaction against the sudden motion of the one-tooth sprocket 10 at the time of engagement sends the planet gear 7 flying.
If the planet gear 10 is sent flying toward the rewinding gear 2 with these causes, and it meshes with the rewinding gear 2, the fork gear 1 rotates at a predetermined rate. The film 3 is pulled in accordance with the difference between the rotation rates of the spool 4 and the fork gear 1, and in the worst case the film loading operation is stopped.